Interface Integrity in Stretchable Electronics

Abstract

Stretchable electronic devices enable numerous futuristic applications. Typically, these devices consist of a (metal) interconnect system embedded in a stretchable (rubber) matrix. This invokes an apparent stretchability conflict between the interconnect system and the matrix. This conflict is addressed by shaping the interconnects in mechanistic patterns that bend and twist to facilitate global stretchability. Metal-rubber type stretchable electronic systems exhibit catastrophic interface delamination, which is investigated in this research. The fibrillation process occurring at the delamination front of the metal-rubber interface is investigated through in-situ SEM imaging of the progressing delamination front of peel tests of rubber on copper samples. Results show that the interface strength is dependent on the delamination rate and the interface roughness. Additionally, the fibril geometry seems highly dependent on the interface roughness, while being remarkably independent on the delamination-rate.

Direct Residual Stress Identification during Machining

“…The interested reader may refer to [21] for detailed calculations of L and M. The convergence criterion of the DIC algorithm is often defined by the value of the Euclidean norm of δλ k compared to a threshold value C Crit , chosen here to be equal to C Crit = 10 −6 [21]. The set of shape functions U is then defined in order to iteratively compute the updated quantity δλ k .…”

Analysis of stress concentration phenomenon in stretchable interconnects

“…The metal used in this study was copper and a nonlinear elasto-plastic model was employed with Young's module, E = 85 Gpa, the yielding point at y = 200 Mpa [17]. The elasto-plastic curve of the metal is demonstrated in Fig .…”